1. Field of the Invention
The invention relates to a method for producing an antifuse in a substrate, in particular in an integrated circuit, and an antifuse structure for integration in an integrated circuit.
2. Description of the Related Art
Antifuse structures are used in integrated circuits to permanently store setting values. For this purpose, antifuse structures can be programmed by being changed over from a high-impedance to a low-impedance state by means of an applied programming voltage. The high-impedance and low-impedance states are permanent, i.e., they are maintained permanently without the presence of a voltage. In this way, the antifuse structure can serve as a binary storage element, the two states being determined by the high-impedance state and the low-impedance state.
Antifuse structures usually have a first conductive region and a second conductive region isolated from one another by a dielectric. The dielectric forms a thin layer between the first conductive region and the second conductive region, which layer is initially nonconductive, or at high impedance. When a programming voltage is applied, an electric field forms between the two conductive regions, a breakdown channel forming at that location in the dielectric at which the breakdown field strength of the dielectric is exceeded by the electric field, which breakdown channel permanently alters the dielectric in such a way that a low-impedance channel is formed.
Conventional antifuse structures are usually produced by stacking layers one on top of the other, the method steps of deposition of a first conductive layer, patterning of the first conductive layer, deposition of a dielectric layer, patterning of the dielectric layer and deposition of a second conductive layer and patterning of the second conductive layer essentially being carried out one after the other.
In order to deposit said layers one above the other, relatively large overlay tolerances are necessary, with the result that when the feature sizes of the integrated circuit are miniaturized, the layers of the antifuse structure cannot be miniaturized to the same extent.